APPLICANT'S ABSTRACT: The proposed research will test the hypothesis that some of the acute and chronic effects of ethanol are mediated by neurotensinergic processes and that individual differences in innate sensitivity to ethanol are governed, in part, by differences in neurotensin levels and receptor densities. These studies will utilize quantitative genetic strategies coupled with biochemical, behavioral and pharmacological approaches. Specific aims include investigations to confirm chromosomal localizations, by quantitative trait locus (QTL) analyses, of genes that regulate ethanol-related behaviors and neurotensin (NT) receptor densities and NT-immunoreactivity (NT-ir) levels. Preliminary evidence suggests significant overlap of QTLs for ethanol- induced locomotor activation, ethanol preference, and hypnotic sensitivity with QTLs for NT receptor density and NT-ir levels. These findings will be confirmed using genetically segregating populations of F2 mice derived from inbred strains. These studies will include genotyping F2 mice with selected polymorphic markers as well as determining ethanol-related behaviors and NT measures in the same mice. Probes for specific candidate genes, including the NT precursor and NT receptor genes as well as markers for simple sequence length polymorphisms (SSLP) will be used in these studies. Other specific aims will examine the role of NT receptors and endogenous NT, in specific brain regions, in mediating ethanol-related behaviors by determining how inhibition of NT receptor synthesis and administration of NT receptor antagonists alter locomotor, and hypnotic, and hypothermic effects of ethanol. The effects of inhibiting NT synthesis and altering levels of the peptide on ethanol-induced locomotor activation, hypnotic sensitivity, and hypothermia will be determined. Inhibition of synthesis of NT or it's receptors will require synthesis and central administration of specific antisense oligonucleotides. Other experiments will be conducted to quantify effects of acute and chronic ethanol administration on NT mRNA levels and to determine the effects of chronic ethanol exposure on NT receptor mRNA levels in specific brain regions. Alcoholism and alcohol abuse continue to be major health problems, and these studies will provide valuable information regarding the neurochemical basis for acute and chronic actions of ethanol. Substantial evidence supports a genetic component for alcohol abuse and alcoholism and the proposed studies will extend our knowledge of cellular and molecular processes mediating differential sensitivity to the effects of ethanol. Identification of mediators of ethanol action in the CNS, particularly in brain areas associated with the mesolimbic system, will assist in understanding, mechanisms underlying the reinforcing effects of alcohol and thus its potential for abuse. Genetic differences in the effects of ethanol on these processes might account, in part, for the known genetic differences in susceptibility to alcoholism.